Such a vehicle heater is known from DE 10 2005 001 662 A1. The hot combustion waste gases leaving the flame tube at the outlet end area thereof are deflected outwardly in the radial direction in relation to the longitudinal axis by the bottom area of the heat exchanger body, which said bottom area is located opposite said outlet end area and enter the backflow space in an inlet area, which is formed between an outer circumferential surface of the flame tube in the outlet end area thereof and the radially opposite inner circumferential surface of the circumferential wall of the heat exchanger housing. The circumferential wall of the heat exchanger housing is expanded in a stepped manner in an expansion area following said inlet area. Beginning with this expansion area, heat transfer ribs are provided on the inside of the heat exchanger housing or of the circumferential wall of said heat exchanger housing, which inside faces the flame tube, in order to transfer the heat being transported in the combustion waste gases to the circumferential wall to a greater extent. The flame tube is also expanded in a stepped manner in the area of the stepped expansion of the circumferential wall of the heat exchanger housing, and both the flame tube and the circumferential wall are made rotationally essentially symmetrical in relation to the longitudinal axis, i.e., they have the same circumferential expansion in all circumferential areas or have the same radial distance from the longitudinal axis.
DE 199 26 264 A1 discloses a vehicle heater, in which the bottom area of the heat exchanger housing is made asymmetric to homogenize the flow of the combustion waste gases in the waste gas backflow space. A calotte-like bulge, which should cause the combustion waste gases leaving the flame tube to flow into the waste gas backflow space to a greater extent or preferably in this area instead of necessarily following the shortest flow path in the outlet circumferential area, is present in an area located diametrically opposite the waste gas outlet.
DE 197 34 814 C1 discloses a vehicle heater, in which the flame tube is arranged eccentrically in relation to the circumferential wall of the heat exchanger housing due to the fact that the height of heat exchange ribs provided on an inside of the heat exchanger housing changes over the circumference. Thus, a smaller volume is made available for the flow through the combustion waste gases in the area of the circumference in which the outlet is provided due to the shorter radial distance present between the circumferential wall of the heat exchanger housing and the flame tube.